HVAC-Talk site will be slow for the next few days. It's normal site/server maintenance. Thx -Dad

Welcome to HVAC-Talk.com, a non-DIY site and the ultimate Source for HVAC Information & Knowledge Sharing for the industry professional! Here you can join over 150,000 HVAC Professionals & enthusiasts from around the world discussing all things related to HVAC/R. You are currently viewing as a NON-REGISTERED guest which gives you limited access to view discussions

To gain full access to our forums you must register; for a free account. As a registered Guest you will be able to:

Participate in over 40 different forums and search/browse from nearly 3 million posts.

Duct in Attic insulation.

I am about to install my first Attic air handler and duct work. I know the duct has to be insulated. Is there a "standard" size to the insulation in R value? I will be using metal ducting. What other precautions should I take with this installation? Any suggestion are welcome. I have done far too many installations of furnace systems but have always stayed away from the attic jobs, leaving them to the younger guys. But this job is for family.
Thanks.

Even in Canada

make sure that the duct is not buried in or even sittting on top of the attic INSULATION. I understand there is even RH in CAN.
Seems I remember some hot days in August competing in St Catharine's Henley Races

You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

Take some furnace/bailing wire with you. Spin the duct in the wire after you wrap it. It relieves the stress on the tape, and helps hold it together longer.

Really good idea about the bailing wire..Thanks.
We do have heavy humidity here in the summer. A suggestion was made that the duct insulation should be the same as the attic insulation. In this case the attic will be insulated to R40. This seems to be the new standard for blown in insulation here.
I like the idea of the 3/8 bubble wrap insulation. Maybe on top of the foil-back and this would insure that the duct is properly insulated.
Anyone see any problems with that idea?
Thanks I appreciate the help.

[QUOTE=trouble time;12651451]Really good idea about the bailing wire..Thanks.
We do have heavy humidity here in the summer. A suggestion was made that the duct insulation should be the same as the attic insulation. In this case the attic will be insulated to R40. This seems to be the new standard for blown in insulation here.
I like the idea of the 3/8 bubble wrap insulation. Maybe on top of the foil-back and this would insure that the duct is properly insulated.
Anyone see any problems with that idea?
Thanks I appreciate the help.[/QUOTE

If not sealed air tight between the two vapor barriers it can condensate.

In my neck of the woods the air handlers are in the attic about 70% of the time. Our code was changed in 2010 that all ductwork, regardless of location, has to be insulated to a value of R8.

I definitely would check with the mechanical code for your area in Canada first. Im sure they aren't going to want you to go to R40 like the attic is. If so I'd move somewhere else instead of trying to wrap duct with 10" insulation.

I also wouldn't put another layer of insulation over your original layer because it will trap moisture between the layers and present possible issue.